In one aspect, the present invention provides an inhaler apparatus comprising interior surfaces having contact with a medicament for inhalation, the interior surfaces including the interior of the mouthpiece and the substrate with medicament deposited thereon. According to the invention, at least one of such interior surfaces have indentations or raised areas therein, the raised areas having valleys between them. These surface modifications provide a mechanism for minimizing the area of contact between the medicament and the surfaces of the inhaler, thereby promoting release of the medicament from the inhaler.
Numerous approaches have been taken in the design and manufacture of dry powder inhalers. For example, WO 93/09832 discloses an inhalation device having an elongate carrier of medicament powder, the medicament powder being released after impact from a hammer, the inhalation device having a convoluted channel to deagglomerate the medicament powder.
The disadvantages of the inhalers of the prior art include, for example, the inability of a patient suffering from a respiratory disorder, such as asthma, to inhale with sufficient force to receive an entire dosage. For example, a patient may only be able to generate an air flow rate of about 15 liters per minute. In most dry powder inhalers, the patient""s inhalation supplies the energy required to dispense the medicament from the inhaler. The air flow rate generated by the patient""s lungs significantly affects the amount of medicament that ultimately exits the inhaler and reaches the lungs.
Another disadvantage of the inhalers of the prior art includes the inability to accurately determine the amount of medicament dispensed, since the inhaler may dispense a greater or lesser amount of medicament, depending upon the patient""s air flow rate, for example.
A further disadvantage of the inhalers of the prior art is a problem of agglomeration of the medicament powder. Agglomerated particles generally impact the mouth and throat rather than remaining in the air flow for deposition on the lungs. One of the approaches to remedying this problem has been the provision of tortuous channels in the inhalers of the prior art to promote deagglomeration. This approach suffers from drawbacks, however, such as the deposition of the medicament along the channels, thereby leading to inaccurate dosage dispensing.
Another disadvantage encountered in the inhalers of the prior art is unintended dislodging, in which the medicament is discharged, for example, upon dropping the inhaler.
For the foregoing reasons, there is a need for a dry powder inhaler capable of delivering an accurate unit dosage of medicament at a low flow rate, such as 15 liters per minute, yet which substantially retains the medicament upon impact, such as dropping the inhaler.
The present invention is directed, in part, to an inhaler apparatus comprising interior surfaces having contact with a medicament for inhalation, the interior surfaces including an interior surface of a mouthpiece and a substrate with medicament deposited thereon, at least one of such interior surfaces comprising indentations or raised areas therein, the raised areas having valleys therebetween. In certain preferred embodiments, the interior surface is a surface on a substrate having medicament deposited thereon, and in other preferred embodiments, the interior surface is an interior surface of the mouthpiece of the inhaler. Preferably, both the surface of the substrate and the mouthpiece and any other surfaces having contact with the medicament have indentations or raised areas therein, or any other surface structure for decreasing the area of contact between the selected medicament and the surface.
In preferred embodiments, the width of the indentations or valleys have a diameter that is about 5% to about 20% smaller and more preferably, about 10% to about 20% smaller than a minimum selected particle size to be administered by the inhaler. In certain preferred embodiments, the width of the indentations or valleys have a diameter of about one micron to about 2.5 microns. Preferably, the depth of the indentations or valleys is also smaller than a minimum selected particle size to be administered by the inhaler, and most preferably, the depth is about 5% to about 50% smaller, and more preferably, about 5% to about 20% smaller than a minimum selected particle size to be administered by the inhaler.
In preferred embodiments, the indentations or valleys are substantially regularly spaced throughout the area of the substrate having medicament thereon or throughout the mouthpiece of the inhaler. In certain preferred embodiments, the indentations are substantially linear.
The substrate having the medicament deposited thereon can be of any selected shape, including, in preferred embodiments, a disk or a tape. Preferably, the substrate comprises multiple dosage units of medicament. In preferred embodiments, the medicament is sealed onto the substrate.
In addition to providing surface topology for minimizing the area of contact between the medicament and the surfaces of the inhaler, the surfaces are preferably made of a material having a low surface energy, and more preferably, also having, when uncharged, no substantial van der Waals or electrostatic interaction with the medicament. Furthermore, the material is preferably substantially chemically unreactive with the medicament. Examples of materials that can be used for such surfaces include perfluorinated polymers such as polytetrafluoroethylene (xe2x80x9cTEFLONxe2x80x9d), silicone, silicon alumina ceramic, polymeric photoconductor, polycarbonate, polyimide, polypropylene and polyethylene. In some embodiments, the surface has reacted with a silane, such as fluorosilane or aminosilane, to form a film having a low surface energy. Alternatively, for example, the surface can be treated to apply a perfluorinated polymer film.
Other preferred aspects of the invention include an inhaler apparatus comprising a mouthpiece, the mouthpiece having a wall with an exterior and an interior surface, the mouthpiece further comprising multiple air inlets extending from the exterior to the interior, the inlets each being in communication with a channel, each channel extending from the interior to the exterior of the mouthpiece. Preferably, each channel is positioned at an angle of about 20 to about 70 degrees, and more preferably, about 45 degrees from the wall of the mouthpiece. Preferably, the channels are substantially cylindrical in shape. In certain preferred embodiments, the channels are preferably less than about 5 mm in diameter, such as about 0.1 to about 5 mm in diameter or less than about 0.1 mm in diameter.
Preferably, the interior surface of the mouthpiece further comprises indentations or raised areas therein, the raised areas having valleys therebetween, and the indentations or valleys are preferably substantially parallel to the direction of air flow in the mouthpiece during inhalation. In preferred embodiments, the width of the indentations or valleys is about 5% to about 20% smaller, and more preferably, about 10% to about 20% smaller than the minimum particle size to be administered by the inhaler.
In certain preferred embodiments, the mouthpiece further comprises a shuttering mechanism for selectively closing at least one of the air inlets, such shuttering action preferably being capable of actuation by the patient.
In another aspect, the present invention provides a method of manufacturing an inhaler apparatus, comprising:
(a) providing a substrate having a surface for deposition of medicament, the substrate having indentations or raised areas therein, the raised areas having valleys therebetween;
(b) depositing medicament on the substrate; and
(c) incorporating the substrate into a housing.
Preferably, the deposition is performed electrostatically. Preferably, the medicament deposited on the substrate has a particle size of about one to about fifteen microns. In preferred embodiments, the methods of the invention include sealing the substrate having medicament deposited thereon.